[Successful remission induction with reduced-dose all-trans retinoic acid for acute promyelocytic leukemia complicated by COVID-19].

A 43-year-old man with pancytopenia was diagnosed with acute promyelocytic leukemia (APL). On the first day of induction therapy with all-trans retinoic acid (ATRA) alone, he presented with high fever and was found to have coronavirus disease 2019 (COVID-19) infection by SARS-CoV2 antigen test. While it is generally recommended to delay treatment for APL patients with COVID-19 unless urgent APL treatment is required, this patient needed to continue treatment due to APL-induced disseminated intravascular coagulation (DIC). Considering the challenge of distinguishing between differentiation syndrome (DS) and COVID-19 exacerbation, the ATRA dosage was reduced to 50%. The patient was able to continue treatment without development of DS or exacerbation of DIC, leading to his recovery from COVID-19 and remission of APL.

Tumor lysis syndrome followed by tumor regression after COVID-19 in a patient with chronic lymphocytic leukemia.

Coronavirus disease 2019 (COVID-19) can become lethal in patients with hematological malignancies; however, several cases of tumor regression after COVID-19 have been described, and the precise mechanism behind this paradoxical effect is unknown. Herein, we describe a case of Tumor lysis syndrome (TLS) followed by tumor regression after COVID-19. A 72-year-old woman with untreated chronic lymphocytic leukemia was admitted to our hospital with SARS-CoV-2 antigen-positive pneumonia. On admission, her anti-SARS-CoV-2 spike antibody was negative despite receiving two prior vaccinations. Immediately after admission, she developed confusion and ventricular tachycardia. Laboratory data showed acidosis, hyperkalemia, and a rapid decrease of tumor cells in peripheral blood, and she was diagnosed with clinical TLS. She was transferred to the intensive care unit and received continuous hemodialysis therapy. Although hyperferritinemia and bicytopenia, which suggest a cytokine storm followed, she recovered without steroids and additional COVID-19 treatment in 8 days. 2 months later, CT revealed a marked shrinking of lymphadenopathy, which was compatible with tumor regression after COVID-19. Considering the impaired humoral immunity and abrupt response, direct oncolysis caused by SARS-CoV-2 and cytokine storm-induced cell-mediated immune reaction may have been responsible for this paradoxical effect.

[Multiple microthromboses with autoimmune hemolytic anemia after BNT162b2 mRNA vaccination].

A 68-year-old man was referred to our hospital with dizziness and mild fever one week after receiving the second dose of the COVID-19 mRNA vaccine (BNT162b2). Laboratory tests showed hemolytic anemia and a positive direct Coombs test, and he was diagnosed with autoimmune hemolytic anemia (AIHA). On admission, the patient had impaired consciousness with auditory hallucinations, and a head MRI scan showed multiple high-signal areas on diffusion-weighted imaging, suggesting multiple recent infarctions. Echocardiography also showed decreased wall motion in the inferior and posterior walls. A skin biopsy to investigate the cause revealed many platelets and fibrin thrombi in the capillaries and small veins, which was considered the cause of the organ damage. After starting prednisolone (1 mg/kg) for AIHA, hemolytic anemia as well as impaired consciousness, and decreased wall motion rapidly improved. Microthrombosis after BNT162b2 mRNA vaccination is rare, and autoimmune abnormalities appeared to contribute to onset in this case.

[An elderly patient with lymphoplasmacytic lymphoma successfully treated with low-dose tirabrutinib].

A 93-year-old woman was diagnosed with lymphoplasmacytic lymphoma (LPL) with circulating tumor cells in her peripheral blood after presenting with anemia. LPL progressed eight months later, with anemia worsening and tumor cells increasing to 66% of leukocytes. She began tirabrutinib at a low dose (80 mg daily: 17% of the standard dose) because she preferred to maintain her quality of life (QOL). Within three weeks, she was free of transfusion dependency and had a partial response with the disappearance of peripheral tumor cells. The dosage of tirabrutinib was increased to 240 mg daily because it was well tolerated. She has been on the treatment for 13 months with no adverse effects. Tirabrutinib, a highly selective Bruton's tyrosine kinase inhibitor, has been reported to have promising efficacy for LPL, but it also has a high incidence of dermatological toxicity, which may impair QOL. Low-dose tirabrutinib initiation may be effective and assist elderly patients with LPL in maintaining their QOL.

Relationship between donor-specific HPA-15 antibodies and poor graft function in HPA-15 mismatched cord blood transplantation.

Poor graft function (PGF) is a fatal complication following hematopoietic stem cell transplantation and is influenced by multiple factors, such as donor-specific anti-HLA antibodies, a poor infused CD34+ cell count, and the donor source. Alloantibodies against human platelet antigen 15 (HPA-15) recognize platelet membrane glycoprotein CD109, which is expressed not only on platelets, but also on megakaryocytes and specific hematopoietic stem cells. HPA-15 antibodies are known to induce platelet transfusion refractoriness and neonatal alloimmune thrombocytopenia, but their effects on graft function following hematopoietic stem cell transplantation remain unknown. We encountered a case of HPA-15 mismatched cord blood transplantation with a high HPA-15b antibody titer. Prolonged PGF and megakaryocyte aplasia with sustained high-titer HPA-15b antibodies were attenuated by rituximab therapy, and rapid recovery of hematopoiesis was achieved. HPA-15-compatible platelet transfusions were highly effective for platelet recovery. Methylcellulose assays and megakaryocyte cultures revealed that patient serum inhibited in vitro hematopoietic development from patient bone marrow cells. These results suggest that HPA-15 antibodies might be a cause of PGF and that reducing the HPA-15 antibody titer might improve graft function in HPA-15 mismatched transplantation.

[Development of classical Hodgkin lymphoma in a patient receiving tocilizumab for rheumatoid arthritis].

A 66-year-old woman was being treated with methotrexate and etanercept for rheumatoid arthritis (RA). Because her RA symptoms worsened, her medication was changed to tocilizumab (TCZ), and her symptoms improved. However, one year and six months later, she was referred to our hospital because of fever, cervical and para-aortic lymphadenopathy, and massive lesions of the liver/spleen. She was diagnosed with clinical stage IVB mixed cellularity classical Hodgkin lymphoma (cHL) on the basis of right cervical lymph node biopsy. Immunohistochemically, Hodgkin cells were positive for CD20, CD30, PAX-5, LMP-1, PD-L1, and EBER and were negative for CD5, CD15, and EBNA2. Her fever and lymphadenopathy did not improve after the discontinuation of TCZ. Therefore, she was administered ABVd therapy and achieved complete remission (CR) after six cycles of ABVd therapy. She was found to be alive and in CR on regular follow up till February 2021. To the best of our knowledge, there are limited reports of immunodeficiency-related lymphoproliferative disorders associated with TCZ in literature, and our case may be a valuable report on the association of TCZ with the development of cHL in patients with RA.

Double-Hit Primary Plasma Cell Leukemia with IGH/MYC and IGH/CCND1 Translocations.

Primary plasma cell leukemia (pPCL) is an aggressive variant of multiple myeloma (MM). Immunoglobulin heavy chain (IgH) translocations are found in a majority of pPCL cases, supporting a central relation to pathogenesis of pPCL. However, two independent IgH translocations are barely detected at the onset of pPCL, and their significance is yet to be elucidated. Here, we report a case of an aggressive pPCL with simultaneous IGH/MYC and IGH/CCND1 translocations. A 73-year-old man was referred to our hospital with back pain and diagnosed as having pPCL with more than 50% circulating plasma cells. Cytogenetic analysis revealed 47, Y, t (X; 8;14) (q24; q24; q32), t (11; 14) (q13; q32), and +18. IGH/MYC and IGH/CCND1 translocations were confirmed by fluorescence in situ hybridization analysis. Bortezomib and dexamethasone treatment achieved rapid elimination of peripheral malignant plasma cells, and the patient maintained a partial response for 18 months. After biological relapse, he received salvage therapy with ixazomib, lenalidomide, and dexamethasone, followed by pomalidomide and dexamethasone, and exhibited stable disease for an additional 14 months. Although IGH/MYC translocation in association with dysregulation of antiapoptotic pathway leads to worse prognosis in lymphomas, the novel agent-based regimen showed good efficacy, suggesting that IGH/MYC plays a different role in the pathogenesis of MM. IGH/CCND1 and IGH/MYC translocations may have contributed to abrupt onset of pPCL in this case.

[Sustained Complete Remission after Eradication Therapy in A Helicobacter pylori-Negative Cecum Mucosa-Associated Lymphoid Tissue Lymphoma].

Most primary gastric mucosa-associated lymphoid tissue(MALT)lymphomas are associated with a chronic Helicobacter pylori(H. pylori)infection. The eradication of H. pylori is the first-line treatment for H. pylori-positive cases with early-stage disease. In addition, successful treatment of H. pylori-negative early stage MALT lymphomas by eradication has been reported in several small cases series. However, the association of primary gastrointestinal MALT lymphomas with H. pylori in areas other than the stomach is not clear, and the efficacy of eradication therapy for these patients has not been established. We performed H. pylori eradication therapy for H. pylori-negative cecum MALT lymphoma. Three months later, a histopathological examination showed no evidence of MALT lymphoma, and the patient was classified as being in remission. So far, the patient has been in remission for 1 year and 6 months. Our case is the first report of successfully treating H. pylori- negative cecum MALT lymphoma with eradication therapy.

[Leucovorin Administration Allows Continued Pralatrexate Treatment in a Patient with Angioimmunoblastic T-Cell Lymphoma].

Pralatrexate(PDX)has been approved for the treatment of relapsed/refractory peripheral T-cell lymphoma(PTCL), including angioimmunoblastic T-cell lymphoma(AITL). Oral mucositis is the most common and severe adverse effect of PDX that often leads to dose reduction or omission. Herein, we report a 65-year-old man with AITL, who received PDX treatment after a second relapse. This drug was effective; however, the adverse effects, such as oral mucositis, were severe. Therefore, leucovorin(LV)was administered to prevent the adverse effect, resulting in continuation of the PDX treatment for 8 months. LV administration minimizes adverse effects for patients receiving high-dose methotrexate. However, the optimal dose and schedule of LV in PDX treatment has not yet been established. In the future, clinical trials on the use of LV for PDX-induced oral mucositis are needed.

Invasive candidiasis leading to gastric perforation in an immunocompromised patient.

Invasive candidiasis remains an important cause of mortality and morbidity in patients with underlying diseases. Here, we report a case of gastric perforation due to Candia glabrata infection in a 74-year-old-male with Paroxysmal nocturnal hemoglobinuria (PNH) who received long-term corticosteroid treatment of hemophagocytic syndrome associated with acute cholecystitis. Total gastrectomy was performed, and he was treated liposomal amphotericin B. The patient was extubated successfully on the 2nd postoperative day, but the patient died of Pneumocystis jirovecii pneumonia (PJP). An autopsy revealed that there was a small amount of the cystic form of Pneumocystic jirovecii, but there was not the presence of Candida spp. Concerning the prophylaxis of invasive candidiasis, there is no strong evidence-based data in clinical practice in immunocompromised patients, such as those receiving long-term immunomodulatory therapy or corticosteroids. Our present case suggests the importance of fungal management and may indicate the need for a new approach to the fungal prophylaxis in such patients.

FIP1L1-PDGFRalpha imposes eosinophil lineage commitment on hematopoietic stem/progenitor cells.

Although leukemogenic tyrosine kinases (LTKs) activate a common set of downstream molecules, the phenotypes of leukemia caused by LTKs are rather distinct. Here we report the molecular mechanism underlying the development of hypereosinophilic syndrome/chronic eosinophilic leukemia by FIP1L1-PDGFRalpha. When introduced into c-Kit(high)Sca-1(+)Lineage(-) cells, FIP1L1-PDGFRalpha conferred cytokine-independent growth on these cells and enhanced their self-renewal, whereas it did not immortalize common myeloid progenitors in in vitro replating assays and transplantation assays. Importantly, FIP1L1-PDGFRalpha but not TEL-PDGFRbeta enhanced the development of Gr-1(+)IL-5Ralpha(+) eosinophil progenitors from c-Kit(high)Sca-1(+)Lineage(-) cells. FIP1L1-PDGFRalpha also promoted eosinophil development from common myeloid progenitors. Furthermore, when expressed in megakaryocyte/erythrocyte progenitors and common lymphoid progenitors, FIP1L1-PDGFRalpha not only inhibited differentiation toward erythroid cells, megakaryocytes, and B-lymphocytes but aberrantly developed eosinophil progenitors from megakaryocyte/erythrocyte progenitors and common lymphoid progenitors. As for the mechanism of FIP1L1-PDGFRalpha-induced eosinophil development, FIP1L1-PDGFRalpha was found to more intensely activate MEK1/2 and p38(MAPK) than TEL-PDGFRbeta. In addition, a MEK1/2 inhibitor and a p38(MAPK) inhibitor suppressed FIP1L1-PDGFRalpha-promoted eosinophil development. Also, reverse transcription-PCR analysis revealed that FIP1L1-PDGFRalpha augmented the expression of C/EBPalpha, GATA-1, and GATA-2, whereas it hardly affected PU.1 expression. In addition, short hairpin RNAs against C/EBPalpha and GATA-2 and GATA-3KRR, which can act as a dominant-negative form over all GATA members, inhibited FIP1L1-PDGFRalpha-induced eosinophil development. Furthermore, FIP1L1-PDGFRalpha and its downstream Ras inhibited PU.1 activity in luciferase assays. Together, these results indicate that FIP1L1-PDGFRalpha enhances eosinophil development by modifying the expression and activity of lineage-specific transcription factors through Ras/MEK and p38(MAPK) cascades.

AML1/RUNX1 works as a negative regulator of c-Mpl in hematopoietic stem cells.

In this study, we analyzed the roles for AML1/RUNX1 in the regulation of the c-mpl promoter. Wild-type AML1 activated the c-mpl promoter through the proximal AML-binding site in luciferase assays using 293T and HeLa cells. In accord with this result, electrophoretic mobility shift assay and chromatin immunoprecipitation assays demonstrated that AML1 bound to this site. Next, we analyzed the function of AML1 using a mutant of AML1 lacking the C terminus (AML1dC), which was originally found in a patient with myelodysplastic syndromes. AML1dC dominant-negatively suppressed transcriptional activity of wild-type AML1. However, unexpectedly, AML1dC-transduced murine c-Kit(+)Sca1(+)Lineage(-) cells expressed c-mpl mRNA and c-Mpl protein more abundantly than mock-transduced cells, which led to the enhanced thrombopoietin-mediated proliferation. Moreover, when AML1dC was induced to express during the development of hematopoietic cells from embryonic stem (ES) cells, AML1dC augmented the c-Mpl expression on hematopoietic stem/progenitor cells. Furthermore, we found that early hematopoietic cells that derived from AML1(+/-) ES cells expressed c-Mpl more intensely than those that developed from wild-type ES cells. In contrast, AML1dC hardly affected c-Mpl expression and maturation of megakaryocytes. As for the mechanism of the different roles of AML1 in the regulation of the c-mpl promoter, we found that AML1 forms a complex with a transcription repressor mSin3A on the c-mpl promoter in hematopoietic stem/progenitor cells, although it forms a complex with a transcription activator p300 on the same promoter in megakaryocytic cells. Together, these data indicate that AML1 can regulate the c-mpl promoter both positively and negatively by changing the binding partner according to cell types.

Direct binding of Lgl2 to LGN during mitosis and its requirement for normal cell division.

The Drosophila tumor suppressor protein lethal (2) giant larvae (l(2)gl) is involved in asymmetric cell division during development and epithelial cell polarity through interaction with the aPKC.Par-6 complex. We showed here that Lgl2, a mammalian homolog of l(2)gl, directly bound to LGN, a mammalian homolog of Partner of inscuteable in HEK293 cells. The C-terminal tail of Lgl2 bound to LGN with a K(d) value of about 56 nm. Endogenous Lgl2 formed a complex with aPKC, Par-6, and LGN. This complex formation was enhanced in metaphase of the synchronized cells by treatment with thymidine and nocodazole. Immunofluorescence staining of the complex was the strongest at the cell periphery of the metaphase cells. Overexpression of the C-terminal tail of Lgl2 induced mis-localization of the nuclear mitotic apparatus protein NuMA and disorganization of the mitotic spindle during mitosis, eventually causing formation of multiple micronuclei. Knockdown of endogenous Lgl (Lgl1 and Lgl2) also induced disorganization of the mitotic spindle, thereby causing formation of multiple micronuclei. The binding between Lgl2 and LGN played a role in the mitotic spindle organization through regulating formation of the LGN.NuMA complex. These results indicate that Lgl2 forms a Lgl2.Par-6.aPKC.LGN complex, which responds to mitotic signaling to establish normal cell division.

Regulation of SNAREs by tomosyn and ROCK: implication in extension and retraction of neurites.

Extension of neurites requires the SNARE-dependent fusion of plasmalemmal precursor vesicles with the plasma membrane of growth cones. Here, we show that tomosyn localizes at the palm of growth cones and inhibits the fusion of the vesicles there, thus promoting transport of the vesicles to the plasma membrane of the leading edges of growth cones. Tomosyn localizes because ROCK activated by Rho small G protein phosphorylates syntaxin-1, which increases the affinity of syntaxin-1 for tomosyn and forms a stable complex with tomosyn, resulting in inhibition of the formation of the SNARE complex. In retraction of neurites, tomosyn localizes all over the edges of the neurites and inhibits fusion of the vesicles with the plasma membrane. Thus, tomosyn demarcates the plasma membrane by binding to syntaxin-1 phosphorylated by ROCK, and thereby regulates extension and retraction of neurites.

Human herpesvirus 6 meningoencephalitis successfully treated with ganciclovir in a patient who underwent allogeneic bone marrow transplantation from an HLA-identical sibling.

Human herpesvirus 6 (HHV-6) has recently been recognized as an important pathogen in immunocompromised hosts, such as patients who have undergone allogeneic bone marrow transplantation (allo-BMT). Here we report a case of HHV-6 meningoencephalitis in a patient who underwent allo-BMT from an HLA-identical sibling. The patient suffered from headache, high fever, tremor, and disorientation on day 35 after allo-BMT. Findings at magnetic resonance imaging, electroencephalography, and routine cerebrospinal fluid (CSF) examination suggested the presence of viral meningoencephalitis. We diagnosed HHV-6 meningoencephalitis by means of polymerase chain reaction (PCR) analysis of a CSF specimen. Successful treatment was achieved with ganciclovir. Because HHV-6 encephalitis has a potentially fatal and fulminant course, it is necessary that HHV-6 encephalitis be recognized as one of the central nervous system complications that can follow allo-BMT. PCR analysis for HHV-6 in the CSF specimen is necessary for appropriate diagnosis and treatment.